When it is desired to provide a magnetron pulsing circuit which is capable of providing different length output pulses from the magnetron, it has previously been customary to use high voltage switching circuits. Thus, the pulse-forming network may be provided with several sections, with the entire pulse-forming network being employed for longer pulses, and only a portion of it being used for shorter duration pulses. The network is divided by a high voltage switching circuit, characteristically a high voltage vacuum relay, which may be selectively closed to permit the longer pulses using the full pulse-forming network, or opened to provide short duration pulses. Unfortunately, high voltage vacuum relays have a limited life expectancy, and their failure requires taking the pulse-forming network out of service while the relay is being replaced.
Accordingly, a principal object of the present invention is to provide a more reliable, variable length pulse-forming circuit, and more particularly one which does not require high voltage switching.
At the high power and high voltage levels which are involved in the present type of circuit, undesired interaction between alternate pulse forming networks feeding a common output pulse transformer and present serious difficulties. Accordingly, an additional object of the present invention is to avoid undesired interaction between two alternate pulse-forming networks which are coupled to single output pulse transformer for triggering a magnetron, or the like.